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The Application Problems of PCA9517 in IIC Bus

user5377549
Prodigy 10 points
Other Parts Discussed in Thread: PCA9517, PCA9515A

Hi, experts.

I have two questions about the application of PCA9517 , 

1) The supply voltage of side A ranges of 0.9V to 5.5V ,  but side B ranges of 2.7V to 5.5V, why is it different ?

     Why we cannot design the IC use the same voltage range?

2)There is a description in the datasheet like below,  why the B side cannot be used in series ?

"This type of design on the B side prevents it from being used in series with the PCA9515A and another
 PCA9517 (B side). This is because these devices do not recognize buffered low signals as a valid low and do
 not propagate it as a buffered low again."

Thanks for your attention.

Ready

  • 0
    TI__Guru 62920 points
    Hello,

    The B side voltage had a higher minimum value since this voltage is also needed to power some of the internal circuitry of the device.

    The reason that B sides cannot be connected together it's because its low level output is higher than its low level input threshold. This is important for the device to support bidirectional signaling, since it allows the device to distinguish between when a device on the B side pulls low versus when a low level is propagating from the A side to the B side.

    Max